Interaction between the Cesium Cation and Cesium Carboxylates: An Extended Cs⁺ Basicity Scale.

Area of Science:

• Environmental Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Cesium mobility in the environment is influenced by interactions with natural organic matter like fulvic and humic acids.
• Understanding these interactions is crucial for predicting radionuclide dispersion and concentration.
• Carboxylic acids serve as models for the functional groups in humic and fulvic acids.

Purpose of the Study:

• To investigate the gas-phase basicity of cesium-polyacid complexes.
• To establish a relative basicity scale for carboxylic acids interacting with cesium.
• To correlate computational predictions with experimental findings.

Main Methods:

• Electrospray ionization of carboxylic acid and cesium salt mixtures.
• Collision-induced dissociation (CID) of [A-Cs+][A'-Cs+]Cs+ clusters.
• Application of the kinetic method to determine relative fragment abundances.
• Density Functional Theory (DFT) calculations for affinity and basicity.

Main Results:

• A gas-phase basicity ladder for carboxylic acid derivatives was constructed.
• Relative basicity data from the kinetic method were calibrated using DFT calculations.
• Polyacid salts exhibited enhanced basicity compared to monoacid salts.
• Substituent effects on aliphatic and aromatic structures were analyzed.

Conclusions:

• The study provides quantitative insights into cesium-ligand interactions in the gas phase.
• Enhanced basicity of polyacid salts suggests stronger interactions relevant to environmental processes.
• DFT calculations effectively complement experimental kinetic data for basicity determination.